This invention relates generally to gas turbine engine variable stator vane assemblies and, more particularly, to an articulating lever arm assembly used with a variable stator vane assembly.
Gas turbine engines include a high pressure compressor, an intermediate pressure compressor, a combustor, a high pressure turbine, and an intermediate pressure turbine. The intermediate and high pressure compressors each include a rotor, and a plurality of stages. The rotor is surrounded by a casing, and each stage includes a row of rotor blades and a row of stator vanes. The casing supports the stator vanes, and the rotor supports the rotor blades. The stator vane rows are between the rotor blade rows and direct air flow toward a subsequent downstream rotor blade row.
At least some known gas turbine engines include at least one variable stator vane assembly that is utilized to control the quantity of air flowing through the compressor to facilitate optimizing performance of the compressor. The variable stator vane assembly includes a plurality of variable stator vanes which extend between adjacent rotor blades. The variable stator vanes are rotatable about an axis such that the stator vanes are positionable in a plurality of orientations to direct air flow through the compressor.
At least one known variable stator vane assembly includes a plurality of variable stator vanes that are each coupled to a respective actuation ring or synchronous ring. More specifically, each variable stator vane is coupled to the actuation ring utilizing a simple lever arm apparatus. For example, at least one known variable stator vane assembly includes a lever having two ends. The first lever end is coupled to a respective stator vane, and the second lever end is coupled to the actuation ring. The second lever end includes a fixed pin, i.e. a pin that is fixedly coupled to the lever second end using a welding or brazing procedure for example. The pin is inserted into the actuation ring and is surrounded by a known journal bushing. During operation, the actuation ring is translated around the engine rotation axis, and the lever arm, coupled between the stator vane and the actuation ring, is moved around an axis that is normal to the engine axis. Since the pin is fixedly coupled to the actuation ring, the rotation of the ring and lever arm creates a moment on the pin that increases torque around the lever arm, thus generating relatively high stresses at the pin end, bushing distress, and/or eventual breakage of the pin.